Screening
At-risk family members
Surveillance for at-risk individuals with a family history of classical familial adenomatous polyposis (FAP) depends on genetic testing results, as described below:
Negative genetic testing: if a person at risk is found not to carry the adenomatous polyposis coli (APC) pathogenic variant responsible for FAP in the family, colorectal cancer screening as an average-risk patient is recommended.[9]
Positive genetic testing: if an APC pathogenic variant is found, regular colonoscopy should be undertaken. Guidelines differ regarding recommended screening intervals; most societies recommend 1-2 yearly surveillance, starting at age 10-15 years.[9][12][29] This should be continued until colectomy is undertaken.[12][29]
No genetic testing: some people who undergo genetic counselling are determined to have a high risk for FAP, but decide, for a variety of reasons, not to undergo genetic testing. These individuals are considered to be potentially at risk and should be offered annual colonoscopy every 12 months, beginning at aged 10-15 years. If results continue to be negative, the surveillance intervals can be extended to every 2 years after 15 years of age. The probability of FAP in a person without any adenomas on annual surveillance begins to decrease around the age of 24 years. This means that surveillance does not need to be as frequent between the ages of 24 and 34 years, and can be even less frequent between the ages of 34 and 44 years.[9]
No familial pathogenic variant found: in some families, pathogenic variants cannot be found with available testing technology. The sensitivity to identify APC pathogenic variants is currently only about 70% to 90%. It should be noted that a test in which no pathogenic variant is identified in an asymptomatic person is not the same as a negative test. Surveillance for these at-risk individuals is identical to that for untested individuals with a known familial pathogenic variant (see above). If polyposis is detected, patients should be managed in the same way as those with a personal history of FAP.[9]
Relatives of patients with attenuated FAP should be offered genetic counselling and testing. If the individual at risk is found to carry the APC pathogenic variant, colonoscopy surveillance should begin at aged 18-20 years, with repeat examinations every 1-2 years.[9][12][29] In the absence of a true negative genetic test result, or if the patient has not undergone genetic testing, they should still begin colonoscopy surveillance in their late teens, with repeat examinations every 2 years. If no adenomas are found, patients should continue with surveillance every 2 years. Multiple surveillance examinations without adenomas at follow-up may warrant longer intervals.[9]
Use of this content is subject to our disclaimer